Methods for assessing remote rockfall hazards above transport corridors

Many roads and railways in Australia, particularly in eastern Australia, traverse steep natural escarpments. These roads are commonly associated with rockfall hazards that pose risks to road users and can also cause significant disruption to these transport assets. The source of these rockfalls can originate considerable distances upslope of roads, often amongst densely forested slopes on steep, mountainous terrain that is difficult to access. Given these constraints it is often difficult for practitioners to assess rockfall hazards and ultimately risks, based on inspections undertaken from within transport corridors and can result in risks being poorly understood. Emerging technologies such as high resolution unmanned aerial vehicle (UAV) mounted lidar acquisition, advances in photogrammetry and three-dimensional rockfall modelling software offer the potential to greatly enhance the understanding of slope processes above roads across large distances. This paper presents the results of a study that investigated the use of a range of technologies aimed at acquiring high quality ground survey data and better predicting the runout behaviour of rockfalls originating from natural escarpments and the likelihood of these reaching a road. This included a detailed study of two large rockfalls above a road in the Sydney Basin. The results of the three-dimensional rockfall modelling are compared with empirical methods traditionally used to predict the runout distance of small rockfalls. When used in conjunction with more traditional engineering geology approaches, the application of emerging technologies can greatly improve the efficiencies and quality of rockfall hazard and risk assessments.